1. Field of the Invention
This invention relates to a propelling mechanism in an intracavity viewing instrument such as an endoscope or a borescope that is adapted to urge the instrument along a narrow and tortuous passage.
2. Description of the Prior Art
Endoscopes are extremely useful in the medical arts for inspecting the interior of certain organs that are otherwise inaccessible to a physician's examination. Hollow viscera, such as the gastrointestinal tract often are required to be inspected for the presence of pathological conditions and diseases. In the physiological state these organs are comprised of long tortuous passageways having flexures and valves that admit of great difficulty in negotiation, even by skilled operators. The splenic and hepatic flexures of the colon and the ileocecal valve are examples of obstacles that can frustrate a medical examination of the bowel. Furthermore friction between the lining of the organ and the instrument limits the distance that the endoscope can be inserted without risking perforation of the organ or damage to the tissues. When these organs become diseased they can be focally or diffusely narrowed. They may also become kinked and structurally weakened so that the passage of the endoscope becomes even more difficult and the risk of perforation and serious injury to the patient increases.
In industrial applications borescopes are highly useful in inspecting the condition of otherwise inaccessible passages, such as the insides of boiler tubes, or hydraulic lines in a turbine or jet engine. These passages also tend to be tortuous. Consequently, because of twists and turns in the passageway, and because of friction between the sides of the insertion tube and the walls of the passageway, the distance into the passageway that the borescope insertion tube can be pushed or pulled is oftentimes limited.
It would be advantageous to provide means on the borescope or endoscope to permit it to advance itself through tortuous passages such as the intestine or curved pipes. Such means would ideally:
(a) produce an axial thrust distributed along the insertion tube to avoid buckling, stretching, or excessive localized insertion tube-wall friction; PA1 (b) be controllable from the proximal end of the insertion tube; PA1 (c) be simple, reliable, and inexpensive to manufacture and maintain; PA1 (d) not substantially increase the diameter of the insertion tube of the borescope; PA1 (e) be capable of operation when only a part of the insertion tube is inserted into the passageway to be inspected; PA1 (f) be applicable to existing borescopes or endoscopes, either permanently or as a removable option; and PA1 (g) be insensitive to the diameter of the passageway in which the borescope or endoscope tube is utilized.
U.S. Pat. No. 4,934,786 to Krauter, having a common assignee herewith, addresses the above problem. In Krauter there is shown an arrangement whereby a pair of elongated bladders is wrapped helically over the insertion tube, configured such that one bladder of the pair expands radially and distally, while the other bladder expands radially and proximally. Compressed air or another fluid is provided periodically to the two bladders such that they are inflated in alternate phase relationship to move the insertion tube in a desired proximal or distal direction. However this arrangement requires a control mechanism to properly phase the supply of fluid to the bladders, and, since there are only two bladders, the motion achieved by alternately inflating the bladders fails to adequately propel the probe under some conditions.